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Hardware and software for 48V battery monitoring

I’ve got a 48V battery system with about 80 Ah (plan to upgrade soon), and need a way to keep track of the power consumed over time. I have a Victron battery monitor but it’s not very useful (only tells me the charge %, which is sometimes wrong, and deepest discharge).

I woke up this morning at 4am with my lithium batteries dead (BMS alarm going off) and without a clue as to why. It would be nice to see a graph of power usage over hours, days, weeks, months, etc. And then a way to notify me (push notification, perhaps) on my mobile phone when I should start thinking of unplugging things, or turning them off. It would be nice to get notified before it’s too late, so I can take appropriate action, and not have my fridge shut off until morning time.

The Solar PV product on OEM’s e-commerce site seems to connect to the AC for power monitoring, and that doesn’t help in my case. I’m using a lot of 12V in my RV and the Victron battery monitor uses a shunt to measure current. It sadly lacks any historical data gathering abilities (unlike their charge controllers). I’d basically like to know what my power usage was, compare it to solar input (connecting to my MPPT controller would be ideal too), and it help me be more conservative with power consumption, before it’s too late and I have no power left.

I’m a mobile app programmer, so I can interface with APIs and come up with my own monitoring app, but one thing I noticed was the Pi devices work via WiFi and I’m wondering if it’s possible to connect via bluetooth instead? I use my phone as a hotspot so I don’t have a router for devices to connect to.